A known power supply system comprises a switching power supply. A low-capacity power supply configured to directly rectify and smooth an AC voltage applied to two capacitors is provided separately from the switching power supply. The low-capacity power supply serves as a power supply for a control circuit when the oscillation of the switching power supply is stopped.
When the oscillation of the switching power supply is started with no power supplied from the low-capacity power supply to the control circuit due to an abnormality in a circuit of the low-capacity power supply, malfunction of the control circuit may possibly be caused by, for example, a signal input from a circuit to which power is supplied at the time of the oscillation of the switching power supply.